Falling film evaporator

ABSTRACT

A falling film evaporator (100), a housing (101) thereof being accommodated with a heat exchange tube (304), a perforated plate (205) and a spraying tube (202), the perforated plate (205) being provided between the spraying tube (202) and the heat exchange tube (304), such that refrigerant sprayed from the spraying tube (202) is sprayed onto the surface of the heat exchange tube (304) by means of distribution of the perforated plate (205); spraying openings (301) on the spraying tube (202) have a strip shape, and the extension direction of the openings is perpendicular to the length direction of the spraying tube (202). By means of configuring the length direction of the spraying tube (202) to be substantially perpendicular to the length direction of the heat exchange tube (304), refrigerant sprayed from the spraying openings (301) flows substantially in the length direction of the housing (101), the flow path of the refrigerant being lengthened, avoiding uneven spraying on the surface of the heat exchange tube (304).

TECHNICAL FIELD

The present application relates to the technical field of falling filmevaporators.

BACKGROUND ART

Falling film evaporators generally use a refrigerant distributor todistribute a refrigerant to the surfaces of heat exchange tubes in aheat exchange tube bundle, so as to form a liquid film for evaporation;they exploit the mechanism of thin-film evaporation from heat exchangetube surfaces, have the advantages of high heat transfer efficiency andsmall refrigerant charge, and have been a focus of research in therefrigeration and air conditioning industries in recent years. However,the uniformity of distribution of refrigerant on the heat exchange tubebundle in the evaporator is a key factor limiting the evaporator's heatexchange performance. The state of refrigerant entering the refrigerantdistributor is generally gas and liquid phases; if the two phases ofrefrigerant are not uniformly distributed onto the heat exchange tubebundle of the falling film evaporator, the result will be that therefrigerant distributor supplies too much refrigerant to a portion ofthe heat exchange tubes and too little refrigerant to another portion ofthe heat exchange tubes, and the phenomenon of “dry spots” will occur,leading to a drop in the overall heat exchange performance of thefalling film evaporator.

SUMMARY OF THE INVENTION

An object of the present application is to provide an improved fallingfilm evaporator, capable of distributing a refrigerant uniformly to heatexchange tubes.

To achieve the above object, the present application provides a fallingfilm evaporator, comprising: a housing, a heat exchange tube, aperforated plate, a spray tube and a liquid entry tube. The housing hasan accommodating cavity; the length direction of the heat exchange tubeis the same as the length direction of the housing; the perforated plateis arranged above the heat exchange tube, and the perforated plate isprovided with multiple distribution holes; the spray tube is arrangedabove the perforated plate, the spray tube having multiple spray ports,the spray ports being distributed at intervals in the length directionof the spray tube, and the spray ports being configured to be capable ofspraying a refrigerant toward the perforated plate; and the liquid entrytube is in fluid communication with the spray tube, such that therefrigerant flowing through the liquid entry tube can flow into thespray tube; wherein the heat exchange tube, the perforated plate and thespray tube are all arranged in the accommodating cavity; and the lengthdirection of the spray tube is substantially perpendicular to the lengthdirection of the housing.

In the falling film evaporator described above, the length direction ofthe perforated plate is the same as the length direction of the housing,and the spray port is configured such that after the refrigerant hasbeen sprayed toward the perforated plate, the refrigerant can flow inthe length direction of the perforated plate.

In the falling film evaporator described above, the bottom of the spraytube has a circular-arc end face, the circular-arc end face protrudingin the direction of the perforated plate, the spray port is in the formof a strip, and at least a part of the spray port is arranged on thecircular-arc end face.

In the falling film evaporator described above, the spray tube has twoextension parts extending in the length direction of the housing, an endof the extension part comprises an outwardly protruding circular-arc endface, the spray port is in the form of a strip, and at least a part ofthe spray port is arranged on the circular-arc end face.

In the falling film evaporator described above, a cross section of thespray tube has a flattened oval shape, the two extension parts arelocated at left and right ends of the spray tube respectively, the sprayport is in the form of a strip, and the spray port extends toward thecircular-arc end faces at the left and right ends of the spray tuberespectively from the bottom of the spray tube.

In the falling film evaporator described above, a cross section of thespray tube has an inverted-“Y” shape, the two extension parts areseparately located at the bottom of the spray tube and extend obliquelydownward, the spray port is in the form of a strip, and at least a partof the spray port is arranged on the circular-arc end face.

In the falling film evaporator described above, multiple said spraytubes are arranged in the falling film evaporator, and top ends of themultiple spray tubes are in communication with each other, so that themultiple spray tubes are in fluid communication with each other.

In the falling film evaporator described above, the number of the spraytubes is an even number, and the multiple spray tubes are distributedsymmetrically relative to the liquid entry tube.

The falling film evaporator described above further comprises a liquidentry box, the liquid entry box being arranged between the liquid entrytube and the spray tube, such that the liquid entry tube and the spraytube can be in fluid communication with each other by means of theliquid entry box.

The falling film evaporator described above further comprises a coverplate, the cover plate being arranged at an upper part of the spraytube, and two side edges of the cover plate extend toward the perforatedplate and are directly or indirectly connected to two side edges of theperforated plate in a sealed fashion.

In the falling film evaporator of the present application, the lengthdirection of the spray tube is configured to be substantiallyperpendicular to the length direction of the evaporator housing; thisconfiguration enables refrigerant sprayed out of the spray ports to movesubstantially in the length direction of the housing, thus extending theflow path of the refrigerant sprayed out of the spray ports, andavoiding the problem of sprayed refrigerant being sprayed unevenly overthe surface of the heat exchange tube due to the flow thereof beinghindered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the three-dimensional structure of afalling film evaporator 100 in an embodiment of the present application.

FIG. 2 is a structural schematic diagram of some of the componentslocated inside a housing 101 of the falling film evaporator 100 shown inFIG. 1.

FIG. 3 is a radial sectional view, at the position of a liquid entrytube 102, of the falling film evaporator 100 shown in FIG. 1.

FIG. 4 is a partial enlarged drawing, in a region of a spray tube 202,of the falling film evaporator 100 shown in FIG. 3.

FIG. 5 is a schematic diagram of the three-dimensional structure of thespray tube 202 in FIG. 2.

FIG. 6 shows a cross section, at the position of a spray port 301, ofthe spray tube 202 shown in FIG. 5.

FIG. 7 shows movement paths of refrigerant after being sprayed out ofthe spray tube 202 with the positional arrangement shown in FIG. 4.

FIG. 8A shows a first embodiment of the cross-sectional shape, at theposition of the spray port 301, of the spray tube 202.

FIG. 8B shows a second embodiment of the cross-sectional shape, at theposition of the spray port 301, of the spray tube 202.

FIG. 9 is an axial sectional view, at the position of the liquid entrytube 102, of a falling film evaporator having two spray tubes 202.

FIG. 10A shows a first embodiment of a structure of two spray tubes inthe falling film evaporator.

FIG. 10B shows a second embodiment of a structure of two spray tubes inthe falling film evaporator.

FIG. 10C shows a third embodiment of a structure of two spray tubes inthe falling film evaporator.

FIG. 10D shows a fourth embodiment of a structure of two spray tubes inthe falling film evaporator.

FIG. 11 shows a comparative embodiment of a positional arrangement of aspray tube inside a falling film evaporator.

FIG. 12 shows an axial sectional view, at the position of the liquidentry tube, of the falling film evaporator having the positionalarrangement of the spray tube shown in FIG. 11.

FIG. 13 shows a radial sectional view, at the position of the liquidentry tube, of the falling film evaporator having the positionalarrangement of the spray tube shown in FIG. 11.

FIG. 14 shows movement paths of refrigerant after being sprayed out ofthe spray tube shown in FIG. 13.

FIG. 15 shows flow rates of refrigerant flowing through differentpositions in the width direction of the perforated plate shown in FIG.14.

DETAILED DESCRIPTION OF THE INVENTION

Various specific embodiments of the present application will bedescribed below with reference to the drawings which form a part of thisSpecification. It should be understood that although terms indicatingdirection such as “front”, “rear”, “upper”, “lower”, “left”, “right”,“top”, “bottom”, etc. are used in the present application to describevarious demonstrative structural parts and elements of the presentapplication, these terms are used herein for convenience of descriptiononly, determined on the basis of the demonstrative orientations shown inthe figures. Since the embodiments disclosed herein may be arranged indifferent orientations, these terms indicating direction are merelyillustrative and should not be regarded as limiting.

FIG. 1 shows a three-dimensional structure of a falling film evaporator100 in an embodiment of the present application. As shown in FIG. 1, thefalling film evaporator 100 comprises a housing 101, a liquid entry tube102, a gas suction tube 104 and tube plates 103. The housing 101 issubstantially cylindrical, and the tube plates 103 are arranged at twoends in the length direction of the housing 101 respectively. The liquidentry tube 102 is arranged at an upper part of the housing 101, andconfigured to guide refrigerant into the interior of the housing 101.The gas suction tube 104 is also arranged at an upper part of thehousing 101, and configured to discharge gaseous refrigerant from thehousing 101.

FIG. 2 is a structural schematic diagram of some of the componentslocated inside the housing 101 of the falling film evaporator 100 shownin FIG. 1, wherein for convenience of illustration, the liquid entrytube 102 located outside the housing 101 is retained in FIG. 2. As shownin FIG. 2, the falling film evaporator 100 further comprises a spraytube 202, a perforated plate 205 and a heat exchange tube bundle 201which are arranged in an accommodating cavity of the housing 101 (shownin FIG. 3). The spray tube 202 is arranged below the liquid entry tube102, the perforated plate 205 is arranged below the spray tube 202, andthe heat exchange tube bundle 201 is arranged below the perforated plate205. The spray tube 202 is substantially in the form of a tube with twoends closed. An inlet 206, configured to be in fluid communication withthe liquid entry tube 102, is provided at the top of the spray tube 202.Multiple spray ports 301 are provided at the bottom of the spray tube202, and are configured to spray refrigerant, which has entered thespray tube 202, onto the perforated plate 205 below the spray tube 202.The perforated plate 205 is substantially in the form of a long strip,and the length direction thereof is the same as the length direction ofthe housing 101. The perforated plate 205 is provided with multipledistribution holes 305, which are configured to redistribute refrigerantsprayed onto the perforated plate 205, so that the refrigerant can beuniformly distributed onto the heat exchange tube bundle 201 below theperforated plate 205. Side stop plates 204 are also provided at left andright opposite sides of the perforated plate 205; the two side stopplates 204 extend downward perpendicular to the perforated plate 205,such that the two side stop plates 204 and the perforated plate 205together form an accommodating space that opens downward. In theembodiment shown in FIG. 2, all of the distribution holes 305 in theperforated plate 205 are round. In other embodiments, the distributionholes 305 may also be of another shape, e.g. oval, square or rhombus,etc. Moreover, the length direction of the spray tube 202 issubstantially perpendicular to the length direction of the perforatedplate 205. That is to say, the length direction of the spray tube 202 isthe same as the width direction of the perforated plate 205. Generally,the length direction of the spray tube 202 is perpendicular to thelength direction of the perforated plate 205, but deviation in thepositional relationship of the two components within a certain range isnot restricted. The spray tube 202 is arranged in a middle position inthe length direction of the perforated plate 205, so that refrigerantsprayed out from the spray tube 202 can be uniformly sprayed from themiddle position in the length direction of the perforated plate 205 totwo sides in the length direction of the perforated plate 205.

The falling film evaporator 100 further comprises a liquid entry box 203arranged between the spray tube 202 and the liquid entry tube 102, and acover plate 302 arranged at an upper part of the spray tube 202. Theliquid entry box 203 extends in the length direction of the spray tube202, and is configured to establish fluid communication between theliquid entry tube 102 and the inlet 206 of the spray tube 202, in orderto enable preliminary distribution of refrigerant in the lengthdirection of the spray tube 202. The cover plate 302 extends in thelength direction of the perforated plate 205, and two side edges of thecover plate 302 extend downward, such that the cover plate 302 appearsas an inverted-“U”-shaped structure. The cover plate 302 is locatedbetween the liquid entry box 203 and the spray tube 202, and is providedwith an opening between the liquid entry box 203 and the spray tube 202,so as to ensure communication between the liquid entry box 203 and thespray tube 202. The spray ports 301 on the spray tube 202 are located ina cavity between the cover plate 302 and the perforated plate 205,thereby ensuring that refrigerant sprayed out of the spray ports 301 canbe guided by the cover plate 302 so as to flow toward the perforatedplate 205.

FIG. 3 is a radial sectional view, at the position of the liquid entrytube 102, of the falling film evaporator 100 shown in FIG. 1. As shownin FIG. 3, the housing 101 contains two heat exchange tube bundles 201,wherein one heat exchange tube bundle 201 is arranged in theaccommodating space formed by the perforated plate 205 and the two sidestop plates 204, and the other heat exchange tube bundle 201 is arrangedat the bottom of the accommodating cavity of the housing 101, each heatexchange tube bundle 201 comprising multiple heat exchange tubes 304.

FIG. 4 is a partial enlarged drawing, in a region of the spray tube 202,of the falling film evaporator 100 shown in FIG. 3. As shown in FIG. 4,the multiple spray ports 301 are arranged at the bottom of the spraytube 202, spaced apart in the length direction of the spray tube 202.The cover plate 302 is connected to the side stop plates 204 in a sealedfashion, so as to ensure that all of the refrigerant sprayed out of thespray ports 301 flows toward the perforated plate 205, and isdistributed, via the distribution holes 305 in the perforated plate,onto the heat exchange tube bundle 201 to undergo heat exchange. Inother embodiments, the cover plate 302 may also be directly connected ina sealed fashion to two side edges in the width direction of theperforated plate 205; such a configuration can likewise ensure that allof the refrigerant sprayed out of the spray ports 301 flows toward theperforated plate 205.

FIG. 5 shows the three-dimensional structure of the spray tube 202 shownin FIG. 2. As shown in FIG. 5, the multiple spray ports 301 are providedat the bottom of the spray tube 202. Each spray port 301 is in the formof a strip, and extends from the bottom of the spray tube 202 toward twoside walls; due to the direction of extension of the openings of thespray ports 301, the plane in which each spray port 301 lies isperpendicular to the length direction of the spray tube 202. Themultiple spray ports 301 are parallel to each other and arranged spacedapart in the length direction of the spray tube 202.

FIG. 6 shows a cross section, at the position of the spray port 301, ofthe spray tube 202 shown in FIG. 5. As shown in FIG. 6, an upper part ofthe cross section of the spray tube 202 is substantially rectangular,while a lower part is substantially a semicircular arc; the spray port301 is located at the position of the semicircular arc at the bottom ofthe spray tube 202, as shown by the blank part at the lower part of thespray tube in FIG. 6. When refrigerant is sprayed out of the spray port301 of the spray tube 202, the refrigerant is spread outward uniformlyin the opening direction of the spray port 301. It can be seen from FIG.5 that the refrigerant sprayed out of the spray ports 301 has a certainflow speed, and due to the fact that the spray ports 301 take the formof long, narrow strips, there is almost no spreading of the sprayedrefrigerant in the length direction of the spray tube 202; most of therefrigerant is sprayed out only in the width direction of the spray tube202.

FIG. 7 shows an axial sectional view, at the position of the liquidentry tube 102, of the housing 101 of the falling film evaporator 100,wherein the arrows indicate the movement paths of refrigerant afterbeing sprayed out of the spray tube 202. As shown in FIG. 7, the coverplate 302, perforated plate 205 and side stop plates 204 have the samelength direction as the housing 101, and are all of substantially thesame length, with all of the ends thereof extending to the tube plates103. Influenced by the shape of the openings of the spray ports 301 andthe pressure difference between the inside and outside of the spray tube202, the refrigerant sprayed out of the spray tube 202 is sprayed into aregion below the spray ports 301 until it reaches the perforated plate205. Since the refrigerant has a high initial speed when sprayed out ofthe spray ports 301, the refrigerant still retains a high speed afterbeing sprayed to the perforated plate 205, thus the refrigerant willflow toward the two ends of the perforated plate 205 in the lengthdirection of the perforated plate 205. The perforated plate 205 is ofadequate length, so the speed of the refrigerant will fall as it flowscontinuously, and when the refrigerant has moved to positions close tothe tube plates 103 at the two sides, the speed of the refrigerant isalready very low, so eddies will not form at the tube plates 103 at thetwo sides, and uniform distribution of refrigerant over the surface ofthe perforated plate is thereby achieved. As the refrigerant moves inthe length direction of the perforated plate 205, the refrigerant canflow from the distribution holes 305 in the perforated plate 205 towardthe heat exchange tube bundle 201 below the perforated plate 205, suchthat the refrigerant is uniformly distributed onto the multiple heatexchange tubes 304 in the heat exchange tube bundle 201.

FIGS. 8A and 8B show cross sections, at the position of the spray port,of two other embodiments of the spray tube 202 respectively. In thesetwo embodiments, the cross-sectional shape of the spray tube 202 isdifferent from the cross-sectional shape of the spray tube 202 shown inFIG. 6. The cross section of the spray tube 202 shown in FIG. 6 islonger in the vertical direction overall, with a narrower transversewidth; the specific manifestation of this is that the upper part isrectangular while the lower part is a semicircular arc. However, whenthe transverse width of the cross section of the spray tube 202 isnarrower, the movement distance of refrigerant in the length directionof the perforated plate 205 will be restricted; thus, in order to enablethe refrigerant sprayed out of the spray tube 202 to move to positionsclose to the tube plates 103 successfully, in some embodiments of thepresent application, the spray tube 202 is extended in the widthdirection of the spray tube 202 (i.e. the length direction of thehousing 101) to form two extension parts 801, and the spray ports are atleast partially arranged on the extension parts, thus helping toincrease the spraying distance of refrigerant in the length direction ofthe housing 101.

As shown in FIG. 8A, the cross section of the spray tube 202 has aflattened oval shape, with flat and straight edges at upper and lowersides, the two extension parts 801 being located at left and right sidesof the spray tube 202 respectively, and an end of each extension part801 having an outwardly protruding circular-arc end face 501; due to thestructure just described, the cross section of the spray tube 202 has alonger transverse span. FIG. 8A shows the position of the spray port 301at the blank part of the cross section of the spray tube; the spray port301 is in the form of a strip, located in the lower half of the spraytube 202, and extends from the bottom of the spray tube 202 toward thecircular-arc end faces 501 at the two sides.

The cross section of the spray tube 202 shown in FIG. 8B has aninverted-“Y” shape; the two extension parts 801 are arranged at twosides at the bottom of the spray tube 202 respectively and extendobliquely downward, such that a certain angle A is formed between thetwo extension parts 801. In some embodiments, the angle A is greaterthan or equal to 60°, so that the transverse width of the spray tube 202is extended to a greater extent. It can be seen from FIG. 8B that an endof each extension part 801 has an outwardly protruding circular-arc endface 501, with spray ports 301 being substantially located on the twocircular-arc end faces 501. FIG. 8B shows two spray ports 301 located onthe same cross section of the spray tube 202. In the length direction ofthe spray tube 202, a row of spray ports 301 is arranged spaced apart onthe circular-arc end face 501 at each side; thus, two rows of sprayports 301 are arranged on the single spray tube 202 shown in FIG. 8B,greatly increasing the spraying distance of refrigerant in the lengthdirection of the perforated plate 205.

FIG. 9 is an axial sectional view, at the position of the liquid entrytube 102, of a falling film evaporator having two spray tubes 202. Asshown in FIG. 9, in order to adapt to a longer length of the housing101, and increase the spraying distance of the spray tube 202 in thelength direction of the housing 101, the embodiment shown in FIG. 9 usestwo spray tubes 202 arranged side by side in the interior of theevaporator housing 101. The cross sections of the spray tubes 202 may beany of the shapes in FIGS. 6, 8A and 8B, and one liquid entry box 203 isprovided above each spray tube 202, such that refrigerant can undergopreliminary distribution in the length direction of the spray tube 202before entering the spray tube 202. To facilitate uniform distributionof refrigerant, the liquid entry tube 102 is arranged in a middleposition in the axial direction of the housing 101, and the two spraytubes 202 are arranged in parallel at the same height above theperforated plate 205, and arranged symmetrically at left and right sidesof the liquid entry tube 102. As shown in FIG. 9, the gap between acenter axis of either one of the two spray tubes 202 in the verticaldirection and a center axis of the liquid entry tube 102 is L, and thedistance between the center axis of either one of the two spray tubes202 in the vertical direction and the tube plate 103 at the sidecorresponding thereto is also L. The symmetric structural arrangement ofthe spray tube 202 that has just been described helps to sprayrefrigerant to the surface of the perforated plate 205 uniformly.

To achieve the abovementioned arrangement of the spray tubes 202, theliquid entry tube 102 in the embodiment shown in FIG. 9 is arranged asfollows: one end, close to a refrigerant inlet, of the liquid entry tube102 is extended vertically; before extending into the housing 101, theliquid entry tube 102 is bifurcated into two branch tubes, which extendhorizontally toward two sides in the length direction of the housing 101respectively; above the positions of the two spray tubes 202, the twobranch tubes are each formed into perpendicular corners and therebyextend vertically downward, until they enter the interior of the housing101, so as to be respectively connected to the two liquid entry boxes203 arranged above the two spray tubes 202. By means of the arrangementjust described, refrigerant is bifurcated into two paths after enteringthe liquid entry tube 102, and flows into the two different spray tubes202 respectively.

In some embodiments, the number of spray tubes 202 may be set to be aneven number greater than two, in order to adapt to a falling filmevaporator having a housing of greater length. Setting the number ofspray tubes 202 to be an even number facilitates the uniformdistribution thereof at the two sides of the liquid entry tube 102, sothat the refrigerant flowing through the liquid entry tube 102 isuniformly distributed to the spray tubes 202.

FIGS. 10A-10D show other embodiments in which two spray tubes 202 aresimultaneously arranged in the falling film evaporator.

As shown in FIG. 10A, the two spray tubes 202 are arranged side by sideat the same height, and share one liquid entry box 203. The liquid entrybox 203 has a wide cross section, so that two side parts in the widthdirection of the liquid entry box 203 can be connected to top ends ofthe two spray tubes 202 respectively, and be in communication with thetop ends of the two spray tubes 202. In the arrangement just described,fluid communication with the two spray tubes 202 can be achievedsimultaneously by means of the shared liquid entry box 203, using onestraight-through liquid entry tube 102; thus, the housing 101 need onlybe provided with one opening for the liquid entry tube 102 to passthrough, thereby simplifying the structure of the liquid entry tube 102and housing 101.

FIG. 10 B shows another embodiment of a double-spray-tube structure. Asshown in FIG. 10B, the two spray tubes 202 are arranged in parallel atthe same height, and the cross section of each spray tube 202 issubstantially round; the round cross section design facilitates uniformscattering of refrigerant in the direction of the spray ports.

FIGS. 10C and 10D show structures in which the two spray tubes 202 arearranged at a certain angle in the falling film evaporator. As shown inFIGS. 10C and 10D, in the same cross section of the falling filmevaporator, the center axes of the two spray tubes 202 form a certainangle B, the angle B being greater than or equal to 60°. This setting ofangle B helps to increase the spraying distance of the spray tubes 202in the falling film evaporator housing in the length direction. In orderfor the center axes of the two spray tubes 202 in the same cross sectionof the falling film evaporator to be configured at a certain angle B,the liquid entry tube 102 is configured such that one end thereof isextended vertically downward, and bifurcated into two branch tubesbefore coming into communication with the spray tubes 202, such that thetwo branch tubes extend horizontally in opposite directions; above thetwo spray tubes 202, the two branch tubes form corners, which are obtuseangles, so that the two branch tubes extend obliquely downward away fromeach other, until they lead into the two spray tubes 202 respectively.

It can be seen from FIGS. 2-10D that in the present application, thelength direction of the spray tube 202 is arranged to be perpendicularto the length direction of the housing 101 of the falling filmevaporator 100, and the spray ports 301 are in the form of strips, suchthat the refrigerant sprayed out of the spray tube 202 can flowsubstantially in the length direction of the housing 101, therebyincreasing the movement space of the refrigerant, such that therefrigerant can be uniformly sprayed onto the surface of the perforatedplate 205. If the manner of arranging the spray tube 202 in the presentapplication is not employed, the movement path of refrigerant afterbeing sprayed out of the spray tube 202 is highly likely to berestricted due to insufficient radial width of the housing 101, with theresult that refrigerant cannot be uniformly sprayed onto the heatexchange tube bundle 201.

FIG. 11 shows a comparative example of a positional arrangement of aspray tube 1202 inside a falling film evaporator. Unlike the embodimentsof the present application, in which the length direction of the spraytube 202 is arranged to be perpendicular to the length direction of theperforated plate 205, in the comparative example shown in FIG. 11 thelength direction of the spray tube 1202 is arranged to be the same asthe length direction of the perforated plate 1205. As shown in FIG. 11,the length of the spray tube 1202 is substantially the same as thelengths of a cover plate 1302, a perforated plate 1205 and side stopplates 1204; the spray tube 1202 is arranged above the perforated plate1205, and a liquid entry tube 1102 and a liquid entry box 1203 are bothlocated above the spray tube 1202. Refrigerant can enter the liquidentry box 1203 from the liquid entry tube 1102, and then be sprayed ontothe surface of the perforated plate 1205 by means of the spray tube1202. The configuration of spray ports 1301 on the spray tube 1202 inthe comparative example is the same as the configuration of spray ports301 shown in FIG. 5 in an embodiment of the present application:multiple spray ports 1301 are parallel to each other and arranged spacedapart at equal distances in the length direction of the spray tube 1202.The difference is that, because the length direction of the spray tube1202 is arranged to lie in the length direction of the perforated plate1205 in the comparative example, the abovementioned configuration of thespray ports 1301 causes refrigerant to move substantially in the widthdirection of the perforated plate 1205 after being sprayed out of thespray tube 1202.

FIG. 12 shows an axial sectional view, at the position of the liquidentry tube 1102, of the falling film evaporator having the positionalarrangement of the spray tube 1202 shown in FIG. 11. As shown in FIG.12, the liquid entry box 1203, spray tube 1202, cover plate 1302,perforated plate 1205 and side stop plates 1204 are all arranged in theinterior of a housing 1101 of the falling film evaporator, and thelengths of the spray tube 1202, cover plate 1302, perforated plate 1205and side stop plates 1204 are substantially the same as the length ofthe housing 1101.

FIG. 13 shows a radial sectional view, at the position of the liquidentry tube 1102, of the falling film evaporator having the positionalarrangement of the spray tube 1202 shown in FIG. 11. As shown in FIG.13, the left and right sides of the falling film evaporator are arrangedsymmetrically, wherein the spray tube 1202 is located in a middleposition in the width direction of the perforated plate 1205, and twoheat exchange tube bundles 1201 are provided below the perforated plate1205, wherein one heat exchange tube bundle 1201 is accommodated in anaccommodating space formed by the perforated plate 1205 and the sidestop plates 1204 at two sides thereof, and the other heat exchange tubebundle 1201 is arranged in a bottom space of the housing 1101, with thelength direction of each heat exchange tube in the two heat exchangetube bundles 1201 being arranged to lie in the length direction of thehousing 1101.

FIG. 14 shows movement paths of refrigerant after being sprayed out ofthe spray tube 1202 shown in FIG. 13. As shown in FIG. 14, therefrigerant sprayed out of the spray tube 1202 has a high initial speed,and when it advances to edge parts in the width direction of theperforated plate 1205, the refrigerant still retains a certaintransverse speed, but the movement path of the refrigerant issubstantially in a radial direction of the housing 1101, and the radialwidth of the housing 1101 is narrow, restricting the width of theperforated plate 1205, thus the perforated plate 1205 does not havesufficient width for the refrigerant to advance further; the refrigeranthaving a certain transverse speed develops eddies at the edge parts ofthe perforated plate 1205 under the blocking action of the cover plate1302, with the result that a greater amount of refrigerant collects attwo sides in the width direction of the perforated plate 1205 than atthe middle position.

FIG. 15 shows flow rates of distributed refrigerant flowing throughdifferent positions in the width direction of the perforated plate 1205shown in FIG. 14. The width of the perforated plate 1205 is limitedbecause the radial width of the housing 1101 is narrow; thus, when thelength direction of the spray tube 1202 is the same as the lengthdirection of the housing 1101, the refrigerant sprayed out of the spraytube 1202 still has a high transverse speed when it reaches the widthedges of the perforated plate 1205, and is therefore restricted inmovement, resulting in uneven distribution of refrigerant in the widthdirection of the perforated plate 1205. As shown in FIG. 15, since thevarious components in the falling film evaporator are arrangedsymmetrically at left and right sides in a radial direction thereof, therefrigerant flow rates are also symmetrical in the width direction ofthe perforated plate 1205 with respect to a center point positionthereof. Specifically, the refrigerant flow rate is smallest at a middleposition located directly below the spray tube 1202, and as the positionis moved toward the two sides in the width direction of the perforatedplate 1205, the refrigerant flow rate gradually increases, with thelargest refrigerant flow rate at the positions of the two edge parts ofthe perforated plate 1205.

As can be seen, in the falling film evaporator of the comparativeexample, the length direction of the spray tube 1202 is configured tolie in the length direction of the housing 1101, such that refrigerantsprayed out of the spray tube 1202 moves substantially in a radial widthdirection of the housing 1101, and because the radial width of thehousing 1101 is narrow, the movement range of the refrigerant afterbeing sprayed out of the spray tube 1202 is greatly restricted, with theresult that the refrigerant cannot be uniformly sprayed onto the heatexchange tubes. In the falling film evaporator 100 in an embodiment ofthe present application, the length direction of the heat exchange tubes202 is arranged to be perpendicular to the length direction of thehousing 101, such that refrigerant sprayed out of the spray tube 202 canmove substantially in the length direction of the housing 101, thusincreasing the movement path of refrigerant, preventing uneven sprayingof refrigerant onto the heat exchange tubes due to movement of therefrigerant being restricted, and thereby avoiding the phenomenon of“dry spots” on the heat exchange tubes caused by uneven spraying ofrefrigerant. Furthermore, the configuration of the present applicationdescribed above increases the movement path of refrigerant in the widthdirection of the spray tube 202, that is to say, the use of theconfiguration of the spray tube 202 in an embodiment of the presentapplication greatly increases the area of coverage when the perforatedplate 205 is sprayed by unit length of the spray tube 202; thus, inorder to achieve a spraying effect for a perforated plate of the samearea, the use of the configuration of the spray tube 202 in anembodiment of the present application greatly reduces the length of thespray tube 202, and correspondingly, the abovementioned configurationalso reduces the number of openings of the spray ports 301 on the spraytube 202, thereby significantly reducing the difficulty and cost ofmanufacturing the spray tube.

Although the present application is described with reference to theparticular embodiments shown in the drawings, it should be understoodthat the falling film evaporator of the present application can havemany variations without departing from the spirit and scope andbackground of teaching of the present application. Those skilled in theart will also realize that there are different ways of changingstructural details in the embodiments disclosed in the presentapplication, all falling within the spirit and scope of this Descriptionand the claims.

1. A falling film evaporator, characterized in that the falling filmevaporator (100) comprises: a housing (101), the housing (101) having anaccommodating cavity; a heat exchange tube (304), the length directionof the heat exchange tube (304) being the same as the length directionof the housing (101); a perforated plate (205), the perforated plate(205) being arranged above the heat exchange tube (304), and theperforated plate (205) being provided with multiple distribution holes(305); a spray tube (202), the spray tube (202) being arranged above theperforated plate (205), the spray tube (202) having multiple spray ports(301), the spray ports (301) being distributed at intervals in thelength direction of the spray tube (202), and the spray ports (301)being configured to be capable of spraying a refrigerant toward theperforated plate (205); and a liquid entry tube (102), the liquid entrytube (102) being in fluid communication with the spray tube (202), suchthat the refrigerant flowing through the liquid entry tube (102) canflow into the spray tube (202); wherein the heat exchange tube (304),the perforated plate (205) and the spray tube (202) are all arranged inthe accommodating cavity; and the length direction of the spray tube(202) is substantially perpendicular to the length direction of thehousing (101).
 2. The falling film evaporator as claimed in claim 1,characterized in that: the length direction of the perforated plate(205) is the same as the length direction of the housing (101), and thespray port (301) is configured such that after the refrigerant has beensprayed toward the perforated plate (205), the refrigerant can flow inthe length direction of the perforated plate (205).
 3. The falling filmevaporator as claimed in claim 1, characterized in that: the bottom ofthe spray tube (202) has a circular-arc end face (501), the circular-arcend face (501) protruding in the direction of the perforated plate(205), the spray port (301) is in the form of a strip, and at least apart of the spray port (301) is arranged on the circular-arc end face(501).
 4. The falling film evaporator as claimed in claim 1,characterized in that: the spray tube (202) has two extension parts(801) extending in the length direction of the housing (101), an end ofthe extension part (801) comprises an outwardly protruding circular-arcend face (501), the spray port (301) is in the form of a strip, and atleast a part of the spray port (301) is arranged on the circular-arc endface (501).
 5. The falling film evaporator as claimed in claim 4,characterized in that: a cross section of the spray tube (202) has aflattened oval shape, the two extension parts (801) are located at leftand right ends of the spray tube (202) respectively, the spray port(301) is in the form of a strip, and the spray port (301) extends towardthe circular-arc end faces (501) at the left and right ends of the spraytube (202) respectively from the bottom of the spray tube (202).
 6. Thefalling film evaporator as claimed in claim 4, characterized in that: across section of the spray tube (202) has an inverted-“Y” shape, the twoextension parts (801) are separately located at the bottom of the spraytube (202) and extend obliquely downward, the spray port (301) is in theform of a strip, and at least a part of the spray port (301) is arrangedon the circular-arc end face (501).
 7. The falling film evaporator asclaimed in claim 1, characterized in that: multiple said spray tubes(202) are arranged in the falling film evaporator (100), and top ends ofthe multiple spray tubes (202) are in communication with each other, sothat the multiple spray tubes (202) are in fluid communication with eachother.
 8. The falling film evaporator as claimed in claim 7,characterized in that: the number of the spray tubes (202) is an evennumber, and the multiple spray tubes (202) are distributed symmetricallyrelative to the liquid entry tube (102).
 9. The falling film evaporatoras claimed in claim 1, characterized in that: the falling filmevaporator (100) further comprises a liquid entry box (203), the liquidentry box (203) being arranged between the liquid entry tube (102) andthe spray tube (202), such that the liquid entry tube (102) and thespray tube (202) can be in fluid communication with each other by meansof the liquid entry box (203).
 10. The falling film evaporator asclaimed in claim 1, characterized in that: the falling film evaporator(100) further comprises a cover plate (302), the cover plate (302) beingarranged at an upper part of the spray tube (202), and two side edges ofthe cover plate (302) extend toward the perforated plate (205) and aredirectly or indirectly connected to two side edges of the perforatedplate (205) in a sealed fashion.